1. Field of the Invention
The present invention concerns a data display system for optically displaying data related to the operation of a vehicle such as a travel speed, an engine speed and a remaining amount of fuel in the form of a light image at a location where a driver of the vehicle can see it, and more particularly, to a system for displaying the above data in a forward visual field of the driver of the vehicle of the type on which, for example, as in motorcycles, the driver rides while wearing a helmet.
2. Description of the Prior Art
Generally, the data related to the operation of a motorcycle is indicated on the instruments installed in the vicinity of a handlebar of the motorcycle. Due to the configuration of the motorcycle, these instruments cannot be positioned in the forward visual field of the driver. Thus, the driver cannot turn his eyes away from the forward visual field to view these instruments while driving, since it is very dangerous. Accordingly, one may conceive to project optically the above data in the forward visual field of the driver by data projecting means provided on the helmet of the driver.
There also is the same problem in the field of aircraft. In order to resolve this problem, Japanese Patent Public Disclosure No. 51-132600 proposes to install optical data projecting means on a helmet of the aircraft pilot. In the data display system disclosed in the above Japanese Patent Public Disclosure, an optical data source, a prism and a half mirror imaging member are installed on the helmet of the pilot. The optical data source converts information to be displayed into light display signals which then are projected in overlapping relationship with a distant view by means of the prism and the imaging member.
The helmet of the pilot normally includes a communication headphone and a microphone which are connected to the airborne communication equipment through an electrical cord. Similarly, in case of the data display system, a transmitter may be disposed on the aircraft and connected to an optical data source by an electrical cord to transmit signals to it. In case of aircraft, the cord connection described above may not necessarily be an obstacle to the pilot since he does not get on and off frequently, and in principle, does not take off his helmet during flight. Additionally, such a cord can also be used to supply electric power from airborne electric power supplies to the optical data source on the helmet. Thus, the problem for the supply of electric power will not occur. However, in case of vehicles such as motorcycles, the driver gets on and off frequently, and the driver must unadvantageously connect and disconnect the cord of the helmet each time he or she gets on and off the vehicle. Furthermore, if the cord comes off from the helmet when running, it would be impossible for the driver to reconnect the cord while driving the vehicle.
The present invention intends to resolve the problems described above for vehicles such as motorcycles on which the driver rides while wearing a helmet. It is an object of the invention to provide a data display system for optically projecting data related to the operation of the vehicle, in a forward visual field of the driver wearing the helmet which is not necessary to be connected to the vehicle by a cord.